Method of and apparatus for locating an identification mark attached to a written orprinted item



March 15, 1960 s-r m ucH 2,928,949

METHOD OF AND APPARATUS FOR LOCATING AN IDENTIFICATION MARK ATTACHED TOA WRIT-TEN 0R PRINTED ITEM Filed July 5, 1957 3. f i A v F I g. I

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INVENTOR ATTORNEY METHOD OF AND APPARATUS FOR LOCATING AN IDENTIFICATIONMARK ATTACHED TO A WRITTEN R PRTNTED ITEM Karl Steinbuch, Fellbach,Germany, assignor to International Standard Electric Corporation, NewYork, N.Y., a corporation of Delaware Application July 5, 1957, SerialNo. 670,111

Claims priority, application Germany July 13, 1956 3 Claims. (Cl.250-206) oddly. In such a case the double pulses of adjoining lines donot start simultaneously with respect to the beginning of the item, butare staggered from lineto line, whereby however, the inset points willlie on one straight line when they indicate an identification mark.

In the following, the invention will be particularly described by way ofexample; as an item, there was been chosen a letter, on which thelocation of the postage stamp is required to be determined. Fig. 1 showsthe the position of mail items is necessary in the course of processesin which the items have to be sorted in accordance with their respectiveplaces of destination, because they are generally capable of assumingone of four different positions, and the sorting can only be performedwhen the mail items are in a proper readable position.

Various methods have already been suggested for sensing and locating thepostage stamps, which are aflixed to letters, by a mechanical scanningoperation. Thereby, in one such known arrangement, the letters are e.g.led past a photo-electric scanning device, in which the scanning beamsweeps forwardly and backwardly vertically in relation to the directionin which the letters travel. As soon as the identification mark (stamp,etc.) is hit by the scanning beam, there is produced in the scanningdevice, e.g. in a photocell, an intensity fluctuation, which may then beused for characterizing the identification mark.

These intensity fluctuations of the photocell current may also beproduced when the photocell is stationary and the mail item iscontinuously led past the cell. However, the evaluation of the intensityfluctuations in this way appears to be somewhat unreliable, because onthe mail items there may also be other markings or signs (such asremarks regarding the address or sender, or the like), and which, undercertain circumstances, may easily cause a similar intensity fluctuationas the identification mark itself.

An object of the present invention is the avoidance of faultyevaluations which may be caused by such other signs, etc. According tothe invention, the items are scanned by means of one or more photocellsrespectively, and the photocell signal, which consists of impulsescorresponding to the brightness variations on the front surface of theitem, will be examined as to the presence of a double impulse, the pulsespacing of which corresponds to the width of the identification mark.The present invention results from the recognition that with the knownmethods of evaluating the difference of the direct-current portionduring the scanning between the item and the identification mark,certain dark-colored letters etc. can not be reliably handled. Thus, forinstance, with some letters the intensity diflerence between thedark'colored envelope and the postage stamps is very small. According tothe invention, therefore, the edges or margins of the identificationmarks are evaluated, whereby, with a suitable design of the evaluatingarrangement, there will be produced a double pulse with a de fined spacebetween the two pulses, which may then be used for identificationpurpose.

In some cases it may be appropriate to carry out the scanning line-wise,that is, the scanning is effected simulintensity fluctuations of thephotocell current, which are likely to appear on the scanning of a darkenvelope. The two large negative pulses correspond to the edges of thepostage stamp. The appearance of such a double pulse is registered by asuitable arrangement or device. Preferably there may be employed atiming-gate circuit, which only produces a control signal, or permitsthe generation of such a control signal whenever two pulses of about thewidth of the postage stamp pass through the gate circuit. In Fig. 2,there is shown such a timinggate circuit, which would meet thisrequirement, and in Fig. Ban alternative arrangement.

' Referring to Fig. 2, the photocell signals coming from the photocell 1are fed via the amplifier 2 to the bandpass filter 3. This filter is sodimensioned that pulses, which correspond to the normal width of thestamp edges, are permitted to pass as strongly and as undisturbed aspossible. The first pulse is fed at the same time to the gate 4 and tothe delay network 5. The gate 4 is a coincidence gate having two inputsand requires the concurrent application of pulses of said inputs tocause it to open. At first the gate 4 is still closed, so that the firstpulse is prevented from passing. In the delay network this first pulseis so delayed that the delayed pulse and the second pulse of the doublepulse appear simultaneously at the gate 4, so that it will now open and,consequently, permit the second pulse to pass. The delay network istuned or adjusted in such a way that in the delay time there arecontained all stamp widths that are likely to occur. Of course, thedelay time also depends on the speed at which the letters travel pastthe scanning device.

The delay network may be of any known type and may consist of e.g. twomono-stable flip-flops which are arranged in series. The first one ofthe flip-flops is excited by the first pulse and is thereby caused totilt into its unstable position. After a delay determined by its timeconstant, it is tilted back to the stable position, and thereby, causesthe second flip-flop to be tilted into its unstable position which also,after its respective time constant, is tilted back. While the secondflip-flop is in its unstable position, the gate 4 is open. The timeconstants are so determined that there will also be obtained a wideningor enlargement of the pulse. This is necessary because different widthsof postage stamps are in use, and because the gate 4 is supposed to bereliably opened to all such widths. In Fig. 3 there is shown anarrangement differing from that of Fig. 2 in that there is provided anadditional arrangement for eliminating the writing in the scanningresults. Due to the fact that the scanning is effected with the aid of agap-type photocell, also all signs etc., such as hand-writing or thelike, will be scanned and fed to the evaluating device. Thereby it mayhappen that in the writing there appear two pulses which are spacedapart each other at a relation lying within therange'of the'stamp width,and which may be so strong that they actually 'can'energize'theevaluating" device. The arrangement'for excluding the writing is nowbased on the experimental fact that the pulses generated by' thewritingare greaterin number" than those pulses which are generated by the stampimage.

The signals as coming from theband-pass'filter 3-of Fig: 2"are fed alsoto the full-Wave rectifier-*6, Fig. 3, and to the low-pass'filter 7. Inthis way,1th'e'inco ming signals are integrated. Upon reaching a'certainvalue the second gate 8 will be blocked. The gate 8 is agate ofknown-typehaving anenabling input 'and'an inhibiting input; The input ofgate 8 which is coupled to the output of gate 4 is the enabling inputand the input to gate'8 which is coupled to the'output of the filter7isfthe inhibiting input. This value is determined in such a manner .thatthe integration. of 'the signals 'producedby the scanning of the'postagestamp'will be insufficient'for blocking or inhibitingthe gate, while theintegration'of the writingsignals for the width of apostage stamp willbe suificient to efiect such blocking. Thus only a double pulse,corresponding to the edges of the stamp, is'capable of transmittingasignal via both gatesii and'S' to the indicating device, in which therecognitionof a posta'ge stampis determined accordingly.

While I'have described above the :principles of my invention inconnection with specific apparatus, it is" to b'e'clearlyunderstood thatthis description is made only b'y'way-of example and not as a limitationto the "scope of my invention as set forth in the objects thereof andinthe accompanying claims.

What is claimed is:

1. Apparatus for determining the position of .a written or printed itemwith respect to an identification mark applied thereto, for example, ofa letter. with respect to thepostage stamp comprising light sensitivemeans for V 4 scanning a surface of said item, means for deriving awave-form linesignal from said scanning means, gate means, time delaymeans intermediate said means for deriving said line signal and saidgate means for delaying said signal a time approximately correspondingto the time taken to scan the Width of said identification mark, meansfor integrating the signals derived from said means for-deriving saidline signal, said integrating means coupled to said gate means wherebysignals corresponding to the edges and the area lying between of saididentificati'on rnark' are ofinsufficient value to prevent opening ofsaid gate means upon application of said edge pulses through saidv delaymeans, but signals derived from extraneous'marking on said item are ofsufiicient value to inhibit :opening of said gate means.

2. Apparatus as claimed in claim 1 wherein said gate means comprisesa'first and a second electronic gate, said first gate comprising atwo-input coincidence gate having-an-output, said second gate having anenabling input and"an'inhibiting input, the inputs of said first gatecoupledto said means for deriving a wave form line signal and'saidtime-delay means, respectively, theenabling'input of said second gatecoupled to the output of said'first gate and the'inhibiting thereofcoupled to the output of said integrating means.

'An apparatus according to claim 1 wherein said integratingmeanscomprises a full-wave rectifier and a lowpass filter'connected inseries.

References Cited in the file of this patent UNITED. STATES PATENTS2,616,983 Zivorykin Nov; 4, 1952 2,760,064 Bell Aug. 21, 1956 2.7771059Stites Jan. 8. 1957 2,824,958 D'unn' Feb. 25, 1958

